A phase II study of anastrazole and fulvestrant in combination with gefitinib in patients with newly diagnosed ER-positive breast cancer

1050 Background: Endocrine therapy for ER+ breast cancer is effective and relatively nontoxic, but is limited by de novo and acquired resistance. Preclinical studies suggest that complete ER blockade along with inhibition of co-expressed growth factor receptors enhances endocrine response and overcomes resistance. Methods: We conducted a phase II trial of combined anastrazole and fulvestrant with gefitinib, an EGFR tyrosine kinase inhibitor, as intial therapy in postmenopausal women with locoregional or metastatic ER+ breast cancer. A tumor core biopsy was done at baseline and after 3 weeks. Patients received treatment for 4 months. Surgery was then offered if the tumor was operable. Primary endpoint was clinical response as defined by RECIST criteria and secondary endpoints were safety/tolerability, complete pathologic response rate (pCR), and biomarker analysis. Planned sample size was 60 patients, but the study closed after 15 patients were enrolled because of poor accrual. Results: Median age at diagn...